Elevated blood hemoglobin on admission as an independent predictor of unfavorable outcomes in patients with aneurysmal subarachnoid hemorrhage

Hemoglobin (HGB), a potent spasmogen, may cause irreversible damage to the brain after aneurysm rupture. However, there is no clinical evidence to reveal the relationship between blood HGB concentrations on admission and the prognosis of patients with aneurysmal subarachnoid hemorrhage (aSAH). We retrospectively reviewed all aSAH patients admitted to our institution between January 2015 and December 2020. Functional outcome was assessed at 90 days after discharge using the modified Rankin scale (mRS). Independent risk factors associated with 90-day unfavorable outcomes were derived from a forward stepwise multivariate analysis. Receiver operating characteristic curve analysis was conducted to identify the best cutoff value of HGB to discriminate 90-day unfavorable outcomes. Then, patients were divided into two groups according to the cutoff value of HGB, and to account for imbalances in baseline characteristics, propensity score matching (PSM) was carried out to assess the impact of HGB on in-hospital complications. A total of 800 aSAH patients without anemia on admission were retrospectively enrolled in this study. Elevated blood HGB (OR= 1.02, 95% CI =1.00-1.03, p = 0.018) on admission was identified as an independent risk factor associated with 90-day unfavorable outcomes, and the cutoff value was 149.5 g/L. After PSM, patients with an HGB > 149.5 g/L had a higher incidence of in-hospital delayed cerebral ischemia (DCI) (33.9% vs. 22.0%, p = 0.013) and deep vein thrombosis (DVT) (11.9% vs. 4.0%, p= 0.006). Patients with a blood HGB > 149.5 g/L on admission might develop more DCI and DVT during hospitalization, leading to 90-day unfavorable outcomes in aSAH patients.